This invention relates generally to radio frequency integrated circuits, and more particularly to a multi-mode RF integrated for use in a mobile radio or similar application.
There is a need for integrated circuits for applications such as mobile radio including but not limited to cellular telephones that can operate in more than one mode. For example, as the mobile radio and cellular telephone infrastructures move from predominantly analog to digital modes of operation, there is a need for mobile radios that operate in both of these modes, analog and digital. Dual mode portable telephones that operate in the cellular and PCS modes of operation allow a user to use the phone in the cellular band of frequencies or in the PCS band of frequencies depending on the user's location.
Dual mode operation also permits the radio frequency integrated circuits (RFICs) to be reconfigured, such as by inserting or removing amplifiers from the received signal path, so that weak signals can be amplified sufficiently by inserting the low noise amplifier in the path, or strong signals can be received without distortion by removing the low noise amplifier from the single path when the received signal strength is adequate for processing without it.
The need for additional functionality in RF integrated circuits, particularly the need for multiple mode RFICs conflicts with the demand for ever smaller systems. Mobile radios generally, and cellular telephones in particular are already very compact, and the demand for ever smaller phones continues to grow.
As phones become smaller, the physical requirements for smaller and smaller RFICs grows as well. One of the requirements for reducing the size of RFICs is to reduce the pin count. Adding additional features, such as multiple modes or functions as, heretofore, required that new control connections and additional pins be added to the IC to select among multiple modes or control the multiple functions. The addition of pins is inconsistent with the reduction in size of RFICs, and it is to this problem the present invention is addressed.